1. Field of the Invention
The present invention relates to a toner used in an electrophotographic method, an electrostatic recording method, an electrostatic printing method, or a recording method according to a toner-jet mode, and to an image forming method.
2. Description of the Related Art
In today's circumstances where there is a world wide, crying need for a reduction in amount of emission of CO2, a technique concerning energy savings has started to be essential. At present, most electric power has been used in a fixing device in a copying device or printer. The use of on-demand fixation that requires small electric power is effective for a reduction in amount of emission of CO2. Such on-demand fixation becomes low-temperature fixation because the on-demand fixation is performed by using a small quantity of heat. In addition, the size and weight of a fixing unit must be reduced in order that the fixing unit may be warmed by using a small quantity of heat. Accordingly, it is difficult to maintain a fixation pressure comparable to a conventional one, with the result that the on-demand fixation becomes low-pressure fixation. Toner has been improved by various approaches in terms of the physical properties of the toner in order that such fixation at low temperature and low pressure may be performed. Of those approaches, a reduction in melting point of a release agent is considered to be effective. However, the use of toner containing a release agent having a low melting point has involved problems such as reductions in development stability and image quality. In particular, a “void” in which part of a thin line becomes void is apt to occur, so the alleviation of the void is necessary. Investigation has been conducted also on the problem of the “void” by various approaches in terms of the physical properties of toner. In recent years, the use of spherical toner has been proposed.
In addition, the digitalization of data has advanced in recent years, so not only the exchange of electronic data but also the reading and digitalization of analog data by using an instrument have been vigorously performed. The kinds of reading instruments cover a broad spectrum including a portable phone and a bar code reader. In a situation where such read symbol is outputted to a medium by using a copying device or a printer and utilized, thin line reproducibility higher than the conventional one is requested nowadays. Meanwhile, the kinds of media to which read symbols are outputted also cover a broad spectrum, so a technique capable of corresponding to output to various media is also important. A technique involving the use of an intermediate transfer member in a transfer step is an example of such technique. However, when an intermediate transfer member is used, the number of times of transfer increases, so a phenomenon in which toner scatters, so called “scattering” is apt to occur. As a result, thin line reproducibility tends to be poor. An improvement has been conducted by various approaches in terms of the physical properties of toner in order that the “scattering” may be alleviated. However, a method of increasing a circularity, the method being effective against the “void”, involves, for example, a problem in that the method is adversely apt to be an aggravating factor of the “scattering”.
In such technical background, at present, toner which: is effective for both the alleviation of a “void” upon low-temperature, low-pressure fixation and the alleviation of “scattering” in a step involving the use of an intermediate transfer member; and shows excellent development stability has been requested. There has been proposed, for example, the suppression of fusion between toner and a member as a technique for improving development stability (JP3002063B). However, it cannot be said that the toner proposed in the document is sufficiently effective against “scattering”, though the toner shows a small degree of aggregation under compression and is considered to be effective for the alleviation of a “void”. In addition, there has been proposed, for example, a toner the degree of aggregation of which under compression is specified as a technique for alleviating a “void” (JP 10-171151 A). However, it cannot be said that the toner is sufficiently effective for the alleviation of the “void”. Moreover, it cannot be said that the toner is sufficiently effective against “scattering”. The toner is considerably susceptible to improvement particularly in a system using an intermediate transfer member.